The purpose of this proposal is to examine the effects of several different classes of toxic substances on murine bone marrow, spleen, and peripheral blood cells using computer-based multiparameter flow cytometry and immunofluorescence. The chemical agents to be studied in this project will include benzene, lead, cadmium, arochlor 1254 (a mixture of polychlorinated biphenyls), hexabromobiphenyl, and benzo(a)pyrene. Previous studies have been shown that these substances are toxic to the immune system, although the primary cell types that are affected have not been determined, and the mechanisms of toxicity have not been elucidated. Multiparameter flow cytometry can be used to characterize the many cell types involved in the immune response, and to assess the effects of toxic substances on a cell by cell basis. Specific subpopulations of murine lymphoid, erythroid, and myeloid-monocytic cells will be identified using a series of rat monoclonal antibodies reactive with cell surface markers. Based upon this identification, the effects of immunotoxic agents will be examined, and the results will be compared with those obtained using functional assays, including progenitor cell assays for bone marrow, mitogenic responses for peripheral blood and the plaque forming response of spleen cells. Multiparameter flow cytometry is likely to provide significant insights into the differential effects of toxic substances on the immune system. In addition, this technology may be used to obtain selected populations of cells through fluorescence activated cell sorting that may be useful in determining the mechanism of action of these agents.